Blame all the lightning strikes happening this summer on the Western Ghats and the Arabian Sea, say a team of scientists at the Centre for Earth Science Studies (CESS).

The two geographical structures that sandwich the state provide the temperature contrast that ultimately leads to the highest incidence of lightning in the country.

Though mountains are a major factor known for the formation of the cumulonimbus clouds (Cb) that cause lightning, R Vishnu, S Murali Das and G Mohan Kumar of the Atmospheric Sciences Division of the CESS have experimentally proved it.

They set up a a field station at Breamore, 800 m above sea-level and at a distance of 40 km from the coast. This had a weather monitoring equipment that would record the temperature, pressure and so on and a lightning detector, that could locate lightning discharges at a radius of 480 km.

"The Cb covering several km are so huge that it requires so much of water vapour. It is the proximity of the sea that provides so much of water vapour," said S Murali Das.

Quite naturally, this means that the Cb clouds were formed on the western side of the Ghats and the station was set at Braemore, on this assumption. With the help of the data in digital data acquisition system, the CESS scientists could provide direct evidence that formation of strong updrafts over a large area with the increase of relative humidity led to lightning and rain nearly one-and-a-half hours later.

The updrafts were at times so strong that the horizontal wind detector did not show any data at all for hours. Apart from the moisture, the other ingredients for the formation of a perfect cumulonimbus cloud is the sea breeze which reaches the mountains in a few hours and push the air upwards.

"Actually the season for lightning activity in the state is from September to June. But in September when you have the monsoon, and during the cooler months you have other bigger systems overshadowing this local activity," said Murali Das.

However, the lightning incidents were a lot less at the mountain tops because another wind from the north-east would blow the clouds to the coast. The coast also showed a slight decrease in lightning strikes compared to the midlands.

"This is because the activity of the cloud peaks and then slows down. Also the activity of the cloud is never more than an hour or so. It dissipates soon after that," said Vishnu.

Also the reason why midranges of the state like Idukki, Kadakkal and Nedumangad have more lightning incidents than the mountains or the coastal areas of Alappuzha and Kochi.